Temperature controlled transmission line

ABSTRACT

A temperature controlled microwave transmission line or waveguide tube. Heating elements are provided along the length of the line and are automatically controlled by thermostatic means to control the temperature within the line to thereby prevent condensation of moisture within the line. The temperature control is in response to temperature both within and outside the line.

United States Patent [191 Elliott et a1.

TEMPERATURE CONTROLLED TRANSMISSION LINE Inventors: Martin K. Elliott, 7838 Rudnick Ave., Canoga Park, Calif. 91304; Michael A. Levin, 5516 Vanalden Ave., Tarzana, Calif. 91356 Filed: July 26, 1971 Appl. No.: 166,023

u.s. c1 333/95 R, 219/366, 219/374, 333/82 BT, 333/83 "r, 219/209 Int. Cl. H0lp 3/12 Field of Search 219/209, 210, 301, 535, 219/366, 374; 333/95, 82 BT, 83 T; 138/103; 343/704 References Cited UNITED STATES PATENTS Fondiller 219/209 X Mar. 12, 1974 3,187,279 6/1965 Hafner 219/209 X 2,760,165 8/1956 Sullivan 219/209 X 2,662,156 12/1953 Potter 219/209 2,955,185 10/1960 Cox 219/209 X 3,474,222 10/1969 Gang 219/210 3,423,570 1/1969 Trabilcy; 219/301 Primary ExaminerRudolph V. Rolinec Assistant Examiner-Saxfiel'd Chatmon, Jr. Attorney, Agent, or Firm-Herzig & Walsh 5 7] ABSTRACT A temperature controlled microwave transmission line or waveguide tube. Heating elements are provided along the length of the line and are automatically controlled by thermostatic means to control the temperature within the line to thereby prevent condensation of moisture within the line. The temperature control is in response to temperature both within and outside the line.

11 Claims, 4 Drawing Figures SUMMARY OF THE INVENTION The invention relates to the field of microwave transmission lines. In the high radio frequency portion of the electromagnetic spectrum, the microwave regions, electrical signals are carried in the interior of hollow metal transmission lines or in coaxial transmission lines, that is lines having a concentric center conductor with a hollow circular metal conductor. Power levels capable of being transmitted within these lines is limited by several parameters, the significant one of which is the moisture content, or the content of other comtaminating vapors in the line. The water vapor can condense in the transmission line forming water pools which cause electrical arcing. The arcs cause signal transmission sections of the line to be inoperative by reason of the change in circuit conditions resulting from the presence of the condensed moisture.

Various methods of eliminating or reducing the vapor content of the air within the transmission lines have been considered and utilized with various, but considerably limited degrees of success. The primary object of the herein invention is to provide means and methods of satisfactorily and successfully eliminating or reducing vapor content in the air within the transmission line. The invention utilizes the basic physical principle of maintaining the temperature of vapor containing gas above the dew point temperature so that the vapors do not condense, but are kept in the gaseous state such that they do not interfere with the operation of the transmission line.

In a preferred form of the invention as described in detail herein, heating elements are provided along the length of the transmission line. The heating elements are controlled by control instruments, preferably thermostats spaced along the length of the line so that the desired result is acheived and the temperature within the line does not drop below the dew point and thus there is no condensation of the vapors. The instruments are dew point controllers in the sense that they serve to maintain temperatures above the dew point.

A further object of the invention is to provide a particular control system for realizing the-primary object of maintaining the temperature along the line above the dew point.

Another object is to provide a preferred system means comprising heating elements spaced along the length of the line and controlled by separate thermostatic devices similarly spaced along the length of the line.

Another object is to provide improved control by way of having the heating elements responsive to temperature conditions both within the line and outside it.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 2 is a cross sectional view of the form of the invention shown in FIG. 1;

FIG. 3 is a schematic circuit diagram of the control system for the heating elements; and

FIG. 4 is a diagramatic perspective view of another form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now more particularly to FIGS. 1 through 3 of the drawings, the transmission line shown may be a typical one. In the exemplary form shown, it is rectangular in cross section and may be constructed of copper or a similar material which is highly electrically conductive. The rectangular tubular copper tube is designated at 10. This part is laminated to another rectangular element having a thicker or heavier wall thickness which may be made of aluminum or brass designated at 12. The metal elements are jacketed by or within heat insulating material 14 which may be of various types which in the preferred form of the invention is a synthetic foam heat insulating material, more particularly, polyurethane which is a commercially available material and one which is easy to fabricate and handle.

Positioned along the lengthof the transmission line are two lines or series of spaced heating elements which in the form of the invention shown are resistance-type electrical heating elements as designated at H1, H2, etc. and H2, H4, etc. These elements may be commercially available heating elements embodying Nichrome wire, for example. The transmission line itself may be of various sizes and cross sections, such as for example, 6 inches by 3 inches or 1% inches by 1 inch. The electrical heating elements are of appropriate size. They might be 6 inch sections closely spaced from each other along the length of the transmission line. Preferably, one line or row of the heating elements is positioned along a top upper corner of the copper tube in a space provided within the heavier metal as shown in FIG. 2. The other line of elements is preferably positioned in a similar space at the lower right hand corner of the tubular member 10. i

The heating elements in the two lines are individually controlled by control instruments for each heating element. The controls for the heating elements may be of standard commercially available types. In the form of the invention described herein, the control instruments are shown as thermostats. The thermostatic controls for each element are as shown, preferably dual thermostats positioned figuratively, backto-back so that one responds to the interior temperature of the transmission line and the other responds to the outside temperature.

FIG. 3 is a preferred circuit diagram of the controls for the heating elements. The thermostats are positioned as described. FIG. 3 shows the circuitry of the section having the electrical heating elements H1 and H3 which are controlled by the thermostats. The thermostats controlling the heater H1 are designated as T1 and T1. The thermostats controlling heater H3 are designated as T3 and T3. The thermostats are shown diagramatically as being of a bimetal type which warp in response to change in temperature to close electrical contacts. Needless to say however, the thermostats could be of various different types. FIG. 2 shows in cross section the physical positions of the heating elements H1 and H3 and the thermostats T1, T1, T3, and T3. The layout or arrangement of heating elements The pairs of dual thermostats have different settings.

In the preferred system, the thermostat responsive to the temperature inside of the line has a lower setting than the thermostat responsive to the outside temperature. The instruments are of course of a type provided with adjustments for setting their control points which is easily done. Settings of the thermostats can easily be made in accordance with teachings herein, that is, to realize the result of keeping the temperature of the vapor within the line above the dew point. Therefore, the settings will depend upon such things as the vapor content or expected vapor content within the line; the amount of insulation on the line; and the environmental conditions. With reference to the electric heater H1, it will be observed that the thermostats T1 and T1 are in parallel, both being in series with the heater H1 so that either one can turn it on. In other words, if the thermostat Tl senses an external temperature which is indicative of a trend which will cause the temperature within the line to fall below the dew point, it can turn the electrical heater H1 on. Also, if thermostat T1 senses a temperature within the transmission line indicating that the temperature is about the fall below the dew point and cause condensation, it will turn the heater H1 on to remedy the matter. The thermostats T3 and T3 coni trolling the heater H3 operate similarly. The electrical heaters preferably are located as shown in the figures.

, From the foregoing, those skilled in the art will readily understand the nature of the construction of the invention, its operating principles, and the manner in which it achieves and realizes the objectives and advantages as set forth in the foregoing. FIGS. 1, 2, and 3 illustrate a preferred exemplary mode of practicing the invention with respect to a transmission line of the type shown. Individual components as described in the foregoing may be selected from components readily available commercially. The length of individual sections of the line, that is, the length of electrical heaters subject to individual control can of course be varied considerably and adapted to specific situations within the teachings embodied herein.

Thermostatic settings are as pointed out above subject to adjustment within the herein teachings.

FIG. 4 shows a modified form of the invention wherein the principles of the invention are applied to microwave coaxial transmission lines. The transmission line shown comprises inner and outer cylindrical metal conductors as designated at and 32. These conductors are made of appropriate materials as conventionally known in the art and may be ofa size normally used for these purposes. The interior coaxial member is supported by diametrical tubular metal supports as designated at 34 and 36 positioned as shown at FIG. 4. Character H designates an electrical heating element which is positioned along the axis of the interior element 30 as shown. Electrical leads as shown at 40 and 42 are connected to the heating element H. Lead 42 is connected to ground, and lead 40 is connected to switchblade 44 which is part of relay 46 having a winding 48. The blade 44 cooperates with a contact 50 as shown. The heating element H is controlled by a thermostat T. It can be conveniently positioned in one of the dielectrical tubular supports 34 as shown. Thermostat T can be of a conventional commercially available type. It controls the relay 46 for turning the heater H on and off. As may be seen, the section of the coaxial transmission line in which the heating element H is contained can readily be controlled so as to maintain the temperature within it above the dew point. Thus, this prevents condensation of vapors within the coaxial line.

Similarly to the previous embodiment of the invention, similar units or heating elements can be provided at spaced intervals along the coaxial line. The spacing is appropriate to control temperature throughout the length of the line to prevent condensation therein. Individual electrical heating elements are controlled by individual thermostats similarly to FIGS. 1, 2, and 3 to maintain the temperature. Dual thermostats such as described in connection with the previous embodiment could of course be used if desired.

From the foregoing and in the light of the description of the previous embodiment, those skilled in the art will readily understand the nature and construction of the embodiment of FIG. 4, itsoperation, and the manner in which it achieves and realizes the objectives of the invention.

The foregoing disclosure is representative of preferred forms of the invention and is to be interpreted in an illustrative rather than a limiting sense, the invention to be accorded the full scope of the claims appended hereto.

What is claimed is:

1. A hollow metal microwave transmission line having means positioned along the length of the line whereby to apply heat for controlling the temperature within the line above the dew point of the vapors contained Within the line whereby to prevent condensation of vapors within the line, said line being of electrically conductive metal and its interior being unobstructed and of a cross section adapted for transmission of high frequency electromagnetic energy.

2. A transmission line as in claim 1, including separate heating elements spaced along the length of the transmission line and thermostatic control means for controlling the heating elements.

3. A transmission line as in claim 2, including separate thermostatic means controlling each individual heating element.

4. A transmission line as in claim 1, including thermostatic elements responsiveto the temperature in the interior of the line-and also to temperature exterior of the line, said elements having different settings which are adjusted to conditions affecting temperature within the line so as to keep the temperature above the dew point.

5. A transmission line as in claim 4, wherein the control means are arranged so that individual heating units can be energized in response to either of the thermostatic means.

6. A transmission line as in claim 1, including ajacket of insulating material surrounding the line, the heating elements being on the interior of the insulating jacket.

7. A transmission line as in claim 1, wherein the line is of a coaxial type having one cylindrical element axially disposed within another cylindrical element.

8. A transmission line as in claim 7, including a heating element positioned within the interior of the inner cylindrical element.

ment which is within the jacket of insulating material.

11. A transmission line as in claim 4, wherein the element responsive to temperature on the inside of the line has a lower setting than the-element responsive to the temperature on the outside of the line. 

1. A hollow metal microwave transmission line having means positioned along the length of the line whereby to apply heat for controlling the temperature within the line above the dew point of the vapors contained within the line whereby to prevent condensation of vapors within the line, said line being of electrically conductive metal and its interior being unobstructed and of a cross section adapted for transmission of high frequency electromagnetic energy.
 2. A transmission line as in claim 1, including separate heating elements spaced along the length of the transmission line and thermostatic control means for controlling the heating elements.
 3. A transmission line as in claim 2, including separate thermostatic means controlling each individual heating element.
 4. A transmission line as in claim 1, including thermostatic elements responsive to the temperature in the interior of the line and also to temperature exterior of the line, said elements having different settings which are adjusted to conditions affecting temperature within the line so as to keep the temperature above the dew point.
 5. A transmission line as in claim 4, wherein the control means are arranged so that individual heating units can be energized in response to either of the thermostatic means.
 6. A transmission line as in claim 1, including a jacket of insulating material surrounding the line, the heating elements being on the interior of the insulating jacket.
 7. A transmission line as in claim 1, wherein the line is of a coaxial type having one cylindrical element axially disposed within another cylindrical element.
 8. A transmission line as in claim 7, including a heating element positioned within the interior of the inner cylindrical element.
 9. A transmission line as in claim 7, including spacer means spacing the inner cylindrical element from the outer element and thermostatic means positioned within a spacer element controlling the heating element.
 10. A transmission line as in claim 6, wherein said line is encased in a further electrically conductive element which is within the jacket of insulating material.
 11. A transmission line as in claim 4, wherein the element responsive to temperature on the inside of the line has a lower setting than the element responsive to the temperature on the outside of the line. 